Microarray Biochip technologies have become central platforms for biological research. The study of gene expression, single nucleotide polymorphism (SNP), comparative genome hybridization (CGH), and protein profiling expression by microarray biochip assays have become standard research techniques. Microarray studies have found a role in both basic and applied research and have also been used in drug discovery, biomarker selection, toxicogenomics, pharmacology, and development of diagnostic and prognostic tests. More recently, microarray-based biochip assays have found a role in clinical diagnostic applications.
Currently, there are major drawbacks with microarray technologies. Despite the fact that microarray technologies have been widely applied over the years and are now considered mature, concerns linger about the consistency and reproducibility of the data from multiple tests. Many investigators are reporting that gene expression data by microarrays is different from other traditional techniques. In addition, debates exist as to whether data from the two different platforms, in situ arrays and spotted arrays, can be compared.
Current processes for manufacturing both array platforms fail to allow for cost-effective customization. Each spot on a microarray requires a discrete deposition or synthesis, both of which are subject to process variation and product control issues that add to the expense and time required for completion. Although microarray and/or alternative approaches permit the measurement of tens of thousands of biological probes simultaneously, they can test only one biological sample at time. This feature is ideal for genome-wide expression profiling, or SNP or protein screening, but is not ideal for applications where a limited number of genes or proteins will be examined for diagnostic purposes, and where testing multiple clinical samples at the same time is preferred. In such a situation, the ability to measure multiple biological samples or duplicate samples simultaneously will increase efficiency, accuracy, and throughput.
Microfluidic technologies are some of the fastest growing sectors in combinative and analytic chemistry, medical devices, and biology. Direct applications can be found in the fields of pharmaceutical development, food testing, clinical diagnostics, forensics, and environmental analysis. Moreover, as these devices are being developed into miniature analyzers (smaller versions of analytical instrumentation), the number of applications is rapidly expanding as the technology advances.
Most microfluidic devices are fabricated with silicon and glass using photolithography, etching, and bonding. These methods are adopted from conventional fabrication techniques used in the semiconductor industry. More recently, hot embossing has been used for complex microfabricated structures.
In microfluidics, traditional materials, such as silicon and glass, are not always the best choice. Also, for some applications, truly three dimensional structures are desired, especially those that possess arbitrary surface height profiles, such as fluidic interfaces. Realization of such structures generally requires multiple lithographic masking and etching, alignment and bonding steps, which add significant process complexity and have implications on reproducibility and yield. Current methods, though highly developed, have some limitations and disadvantages for fluidic device fabrication and construction. Varying depths within the structure on a single wafer is not possible in single step processing, that is, 3D microstructures with high-aspect-ratios are very difficult to achieve. These methods are expensive, as they require clean room processing; photolithographic, etching, and bonding procedures; as well as a silicon, glass, or quartz wafer materials. Consequently, unit costs of microfluidic devices are very high.
In these current microfabrication methods, bonding is an unavoidable processing step that is costly and prone to imperfections. A common drawback with bonding is incomplete bonding of the various areas and regions, which causes microchannel, microchamber, or cavity imperfections, as well as cross leakage. As microstructures become more and more complex, such incomplete bonding becomes an increasingly unwieldy problem.
Assembly of carbon nanotubes from as-grown randomly tangled states into well-ordered arrays has attracted considerable attention from researchers and engineers worldwide due to specific properties of the carbon nanotubes and its importance for chemical, biomedical and engineering applications. Many researches have recently demonstrated the preparation of organized nanotube arrays using effective methods such as wet chemical self-assembly and capillary force induced alignment. For the many applications, well-ordered and functionalized carbon nanotubes are greatly desirable. However, it remains a big challenge and is still at the prototype level.
Accordingly, there is a need for the development of improved fluidic array devices and related methods of manufacturing thereto.